The purpose of this application is to: a) Continue the experimental intercomparison of clinically active fast neutron beam radiotherapy projects in regard to fast neutron dosimetry, b) include new clinical projects in this intercomparison as they become active, c) assist the cancer therapy effort in general and the Radiological Physics Center-Houston in its role as the dosimetry quality control arm of RTOG by development of a fast neutron dosimetry protocol based on the best experience and advice currently available. This protocol would then be subject to review by a suitable scientific body. The field of neutron therapy is in a period of rapid development in facilities of varied backgrounds. This enriches the base of the physics advice and dosimetry methods available but accentuates the need for a mutually agreeable aproach to the dosimetric basis for national clinical trials of fast neutrons at these centers. This task group will ensure the compatibility of current practices at the various facilities by experimental intercomparison of dosimetry at new facilities as they become active and/or at one established facility so that such experimental exchanges occur at least once per year. Subsequent to acquisition of data and dependent upon opportunity for review and evaluation, meetings will be held to compare the data, plan experimental resolution of differences and develop a protocol of significance to the fast neutron beam therapy trials and to the radiological community, irrespective of the centers' relation to any such proposed national clinical trial.